J. Donald CossairtFermi National Accelerator Laboratory

Batavia, ILOperated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359

with the United States Department of Energy.

Posting of Accelerator Enclosures

Presented at the DOE Accelerator Safety Workshop held at SLAC National Accelerator Laboratory, August 2010

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Fermilab Posting Philosophy

10 CFR 835 Requirements• 835.2 Definitions: Those of all “Areas” [e.g.,

Radioactive Material, Radiation, High Radiation (HRA), Very High Radiation (VHRA)] say, “…any area accessible to individuals…”

• 835.502 gives a menu of physical controls for entering HRAs and VHRAs – controls certainly appropriate if such areas are actually entered.

• 835.603 gives standardized postings for “Areas”• 835.604 gives exceptions - We view all,

especially “the less than 8 continuous hour” one, as inappropriate for prompt radiation hazards at accelerators when applied to potential VHRAs.

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Fermilab Posting PhilosophyGUIDANCE DOCUMENTSDOE G 420.2-1 Chapter II, Section B.3.2:

“ii. An exclusion area is an area that is locked and interlocked to prevent personnel access while the beam is on. A fully enclosed and interlocked area is considered inaccessible.” We believe this to be valid.

DOE G 441.1-1C • Definitions: “Occupied (occupiable) area: An area or

location that may be physically accessible by individuals (or body parts thereof) while a radiation-generating device is in operation.” We believe that this does NOT describe accelerator areas as occupiable where access is excluded by interlocks, etc.

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Fermilab Posting PhilosophyGUIDANCE DOCUMENTSDOE G 441.1-1C • 12.2.4 Accessibility “Radiological areas and radioactive material areas are

defined based upon area accessibility. An area is considered to be accessible to individuals when it contains entrance or access points of sufficient size to permit human entry, i.e., such that any portion of the body may be exposed to the radiological hazard.”

“Areas with entrance or access points consisting of locked doors or other controls and interlocks (including those specified under 10 CFR 835.502), should be considered accessible to individuals…”

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Fermilab Posting PhilosophyGUIDANCE DOCUMENTSDOE G 441.1-1C 7.4.1.0 Accelerators“…Although the basic radiological control program requirements discussed in this Guide are generally applicable to the large multi-purpose research accelerators, the complexities associated with these facilities may require additional consideration beyond the scope of this Guide. Additional requirements for those RGDs with particle energies exceeding 10 MeV are provided in DOE O 420.2B, Safety of Accelerator Facilities…”

G441.1-1C specifically refers back to O420.2B and by implication its associated Guide, for “large accelerators”.

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Fermilab Posting PhilosophyFERMILAB PRACTICEFermilab Radiological Control Manual

Article 232.2e: “Accelerator/beamline enclosures to

which personnel access is excluded during operations by the radiation safety interlock system are posted for the radiological conditions anticipated when the beam is off and personnel access is permitted.”

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Fermilab Posting PhilosophyFERMILAB PRACTICEAll areas with primary proton beam areas are posted HRA,

the levels seen when people enter.Most secondary beam areas are posted HRA, a few are RANone are accessed beam-on. PERIOD – no exceptions!Access to these exclusion areas is ALWAYS prevented

using locked doors/gates & hard wired, tested interlocks. These features are covered by the SAD/ASE (O420.2b).No administrative controls; signs, rope-offs, etc. are ever used for this purpose.

Any beam-off accessible areas > 500 rads/hr including those within exclusion areas ARE posted VHRA with access controlled in compliance with 10 CFR 835.

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Fermilab Posting PhilosophyADDITIONAL RATIONALE AT FERMILAB• Tremendous efforts are made to make access

impossible, hence “inaccessible”.• “Robust” interlocks are designed to consensus

standards.• Search and Secure procedures (“sweeps”) assure

clearance of personnel before beam startup.• Reserve VHRA signage for instances when there is

real exposure potential to those dangerous levels.• Want people to SEE VHRA signs when hazard is real!• Door signs also identify other hazards (e.g.,

electrical, cryogenic, ODH). Don’t want people to miss those!